Past vegetation reconstruction and indicator species for guiding endemic flora restoration on the island of St Helena (South Atlantic Ocean)

Abstract Introduction St Helena, an isolated island in the South Atlantic Ocean, has undergone drastic environmental changes since its discovery in 1502, with native vegetation almost completely replaced by introduced species. The disturbed remnants of the native vegetation can provide only limited guidance for habitat restoration. Objectives Our aim is to identify broad patterns in the modern and pre‐anthropic vegetation and to create an indicator species approach for identifying these patterns in the field for restoration purposes. Methods Using partitioning around medoids clustering, Bayesian grade of membership method, and detrended correspondence analysis, we classified broad vegetation zones for modern and pre‐anthropic St Helena. An indicator species analysis was applied to identify these zones in the modern vegetation. Results Despite near‐complete species turnover, the broad zonation (dry, intermediate, and moist zones) remains similar between past and present vegetation, following the island's soil moisture gradient. However, signs of the influx of newly introduced species spreading to and over the island can be seen with closer inspection of the contemporary vegetation. The broad environmental zones are marked by the presence of communities with overlapping species composition. We propose a set of 25 easily identifiable species as indicators for modern vegetation zones. Conclusions Restoration on St Helena requires active planting and maintenance of native species. Our indicator species approach offers a practical tool for defining planting zones. Introduced species can serve as useful indicators for guiding endemic flora restoration.